Iodobenzene compounds having on the benzene ring several iodine atoms, in general 3 iodine atoms per benzene ring and various other substituents, have been used for a long time as contrast agents. These other substituents are pharmacologically acceptable groups which allow administration of the compounds to man and to animals. These substituents are generally chosen, on the one hand, to confer on the compounds a sufficient water-solubility for administering these compounds in aqueous solution and, on the other hand, to confer on these compounds sufficient tolerance by the human body.
To this effect, nonionic compounds, that is to say substituted iodobenzenes possessing nonionic substituents, have been proposed.